Grinding balls.



PATENTED OCT. 22, 1907.

E. G. HOFFMANN. GR'INDING BALLS.

APPLIGATION FILED HAY s. 1907.

/NVENTH 477-0 NEYS W/'TNESSES f PATENT oEEIoE.

ERNST GUSTAV HOFFMANN, F NEW ROCHELLE, NEW YORK.

GRINDING BALLS.

Specification of Letters Patent. L'

Patented oct. '22, 1907.

Application filed May 6, 1907. Serial No. 372,078.

To all whom it may concern:

Be it known that I, ERNsT Gus'rav HOFFMANN, a citizen of the UnitedStates, residing inthe city of New Rochelle, in the State oi New York,have invented certain new and useful Improvements-in Grinding Balls, ofwhich the following is a specification, reference being had to theaccompanying drawing, forming a part hereof.

The grinding of metal balls for ball bearings and other purposes forwhich accuracy, uniformity and high finish are desirable, is commonlyeffected in a oil. chines is not tHe same as the peripheral speed of themachinevrhich comprises two disk-like' plates of metal, relativelyrotatable and pressed yieldingly, one toward the other, concentricgrooves being formed in the adjacent faces of the plates or in the faceof one 4of them in whichthe ballsare received` together with an abrasivepowder, usually emery powder, mixed with The peripheral speed of theballs in such ma- `number ofv scratches whichare sometimes visible to,the naked eye as a sort of cloudiness or dullness upon the surface ofthe ball and are always plainly apparent when the ball is examined with'a microscope 0fmoderate power. The balls finished fin this mannerthereiore leave something to be desired in` the way of smoothness and bythe present invention it has-been discovered that a much greaterapproach to perfect smooth-' ness of surface, as well as almostmathematically perfeet sphericity and accuracy of the vballs can besecured by dispensing altogether with the use oi loose abrasive materialand by carrying on the grinding between two disks or plates; relativelyrotatable and o e or the other provided with concentric grooves asbefore, whileone of such disks or plates is itself composed of abrasivematerial. Especially good results are attained if such particles ofabrasive material as may be loosened fromthe plateor disk as it wearsaway are immediately removed',"as by washing them out with a constantand ample flow of a suitable liquid.

The inventionwill be more fully explained hereinafter with reference tothe-accompanying'drawing in whichl'iis represented so much of a grindingmachine stood, and in which-- f The' whole surface VFigure 1 is a viewin side elevation, partly broken out, of a portion of such a machine,and Fig. 2 is atop view oi the same. l

` In the particular form of mechanism which is chosen for illustrationof the nature of the invention astationary disk A, preferably of metaland having in its working face a s'eries of concentric grooves a, ismounted upon a-stationary shaft B, being held from rotation thereon andalso from longitudinal movement by any suitable means, such as a pinbpassing through the hub of the grinding disk or plate A and the shaftand. removable to permit the disk or plate to be moved hack upon theshaft when necessary.

A rotating disk or plate (l, made of any suitable abrasive material,such as corundurn, for example, is mounted to rotate upon the shaft B,being provided for this purpose, in the machine shown, with a suitable-wheel or belt pulley D. It is pressed toward the plate or 4disk A l yany suitable means, as a stiff spiral spring E surrounding the shaft Band abutting against an adjustable nut e. The pl'ate or disk O may ormay not be provided, when new, with concentric grooves in its workingface, which correspond to the grooves a in the working face of the diskor plate A, but such grooves are naturallyformed therein as the use ofthe machine continues. I

The balls to be ground, which are shown in place in Fig. l, may b eintroduced and removed and interchanged through slots in the disk A andby means of a table G`in spiral form, all as fully explained in LettersPatent of the United States No. 803,164, dated October 3l, 1995, or byany other suitable means. The operation of the machine shown in thedrawing is in general. the same as that of the machine described -insaid Letters Patent, but no emery powder or other loose abrasivematerial is supplied to the machine, the abrasive action of the disk Obeing alone relied upon. If this disk is made of suitable material, itwill 4slowly wear away in an impalpable powder, but to prevent anyscratching of the balls by particles which' may be loosened from thedisk it is desirable that they l be removed immediately. If `thegrinding should be done dry,4 such loose particles would be quicklythrown' out or might be blown out by a .blast of air suitably directed.The grinding, however, is .preferoil Hows through a pipe h to acentrifugal pump I by Which it is returned t'o the grinding disksthrough a piper by which the oil or other liquid is distributed upon thetable G from which it passes With the balls through the disk A to thegrinding surfaces.- By s'uch means the particles of metal and ofabrasive material are immediately removed from the grinding surfaces andthe scratching of the balls thereby is Wholly obviated. V

From the fact that the disk A is provided with a series of concentricgrooves it Will be apparent that the balls do not partake of any radicalmovement `across the disk C of abrasive material during the grindingprocess, from which it follows that in my process the balls alwaystravel in a path or paths concentric with the axis of the rotating diskduring the grinding operation. 'This will result in` slight groovesbeing formed in the abrasive diskl when in use, as above pointed out,whereby the area of contact between the abrasive disk and the balls isincreased and a better' grinding action secured. 1

While the machine herein shown is Well adapted for 'carrying out theinvention, it will, nevertheless7 be understood that thelinvention isnot restricted to any particular form or type of machine and that themechseaseo anism shown and described herein canr be variedhas may befound desirable to meet the necessities of dil ferent uses.

I claim as my invention:

l. The improvement in the method of grinding vballs which consists in4grinding them between relatively rotating disks, while they travel in apath concentric with the axis of rotation one of said disks being formedof abrasive material.

2. The improvement in the method of grinding` balls which consists ingrinding them between relatively rotating disks, While they travel in apath concentric with the axis of rotation, one of said disks beingformed of abrasive material, and in immediately removing the looseparticles of abrasive material.

3.' lhe improvement in the method of grinding balls which consists ingrinding them between relatively rotating' disks, while they travel in aseriesy of paths each corr., centriewith the axis ofmrotation one ofsaid disks being formed of abrasive material, and in constantly washingYout the loose abrasive material by means of a suitable liquid.

Api-i1, A. D., 1907;`

ERNST GUSTAV HOFFMANN.

Signed in the presence of Ammosn L. OSHEA, ELLA J. KRUGER.

This specication signed and Ywitnessed this 26th day of

